One of the few big sources of knowledge on self-development I’ve incorporated is a series of Havard lectures on Positive Psychology by lecturer & author Tal Ben-Shahar.
Each lecture is an hour or more and there are twenty or so lectures in the course. I’ve watched all the lectures at least twice and some of it has stuck with me and has helped me navigate my life in a meaningful way.
The lectures are jam-packed with information on how people who excel at life think. It’s very digestible understandable knowledge and is a large part of the basis of my knowledge in the realm of psychology.
I found these lectures on http://ThePirateBay.org but they have also been uploaded to YouTube.